With the continuous development of the display industry, the requirements for display quality and display effect of thin film transistor (TFT) liquid crystal displays (LCDs) are continuously increased. Existing back light sources require complex structures such as a light guide plate, a light source, and the like, which occupy the space of the display panel. Additionally, the back light source is a separate module and is required to be operationally attached to a TFT substrate, resulting in an increased thickness of the display panel. A commonly-used light source of a daylight lamp contains a mercury medium, which may volatilize due to heating, and may be prone to cause the pollution of mercury vapor.